Hi guys, A good friend of mine want to use his Fi btl n2 15" in a new ported box. He was using mine until I sold the box. This will be a temporary setup, as he is in the process of ordering a second btl, and the box for the 2 is ready (he had 2 Xcons 15" in, before). So, the box he wants to use has those dimensions: 83 cm x 37 cm x 50 cm 32.7" x 14.6" x 19.7" Those are internal dimensions. He has 2 4" flared ports that he wants to use. What length should he make them to achieve a 32 Hz tuning ? Thanks very much for your help. I use to "work" with RAM Design for L port boxes, but I want to try the forum members for these round ports.